The preparation of siloxane-oxyalkylene copolymers ("Copolymers") by the hydrosilation reaction of an organohydrogensiloxane and an unsaturated polyoxyalkylene is well known. The hydrosilation reaction is typically performed in a low molecular weight, highly volatile, hydrocarbon solvent such as benzene, toluene or xylene to compatibilize the reactants and aid in the transfer and filtration of the Copolymer, or to moderate the exothermicity of the hydrosilation. Less typically, the hydrosilation reaction may be conducted without a solvent or conducted in an oxygen containing solvent such as an ether, a polyether, or a lower or higher molecular weight alcohol.
In the majority of the aforementioned processes, the hydrocarbon solvent is removed after the hydrosilation reaction is completed, since in most cases, the solvent is too flammable, toxic or otherwise detrimental to the final product or further processing steps in which the copolymer is utilized. For example, with mono-alcohols in polyurethane foam applications, the hydroxy functionalities will enter into the urethane reaction and act as reaction chain terminators in a detrimental fashion. Removal of said solvents increases batch cycle times and necessitates disposal of the solvent in an environmentally safe manner such as incineration. Moreover, there are foaming problems in removing many solvents and rarely can one get all of the solvent out of solution.
A few instances have been reported in the literature where for one reason or another it was neither necessary nor desirable to separate the copolymer from the reaction solvent. For example, U.S. Pat. No. 4,520,160 discloses the use of saturated higher alcohols, such as isostearyl alcohol, as a reaction solvent which purposely need not be removed from the resulting Copolymer when it is used subsequently in personal care compositions as emulsifiers. U.S. Pat. Nos. 4,857,583 and 5,153,293 also teach that higher boiling point polyols or monocarboxylate esters of an alkanediol purposely need not be removed from the resulting Copolymer when it is used subsequently in polyurethane foam formulations. However, the hydroxy functionality of the solvents may compete with the unsaturated polyoxyalkylene for SiH sites on the siloxane backbone, as well as the above mentioned reaction with the isocyanate in polyurethane foam. It is therefore an object of the present invention to provide an improved process for the preparation of Copolymers using superior solvents.